[Code of Federal Regulations]
[Title 40, Volume 2]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR50.9]

[Page 8-9]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS--Table 
of Contents
 
Sec. 50.9   National 1-hour primary and secondary ambient air quality 
standards for ozone.

    (a) The level of the national 1-hour primary and secondary ambient 
air quality standards for ozone measured by a reference method based on 
appendix D to this part and designated in accordance with part 53 of 
this chapter, is 0.12 parts per million (235 [mu]g/m\3\). The standard 
is attained when the expected number of days per calendar year with 
maximum hourly average concentrations above 0.12 parts per million (235 
[mu]g/m\3\) is equal to or less than 1, as determined by appendix H to 
this part.
    (b) The 1-hour standards set forth in this section will remain 
applicable to all areas notwithstanding the promulgation of 8-hour ozone 
standards under Sec. 50.10. In addition, after the 8-hour standard has 
become fully enforceable under part D of title I of the CAA and subject 
to no further legal challenge, the 1-hour standards set forth in this 
section will no longer apply to an area once EPA determines that the 
area has

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air quality meeting the 1-hour standard. Area designations and 
classifications with respect to the 1-hour standards are codified in 40 
CFR part 81.

[62 FR 38894, July 18, 1997, as amended at 65 FR 45200, July 20, 2000]

    Effective Date Note: At 68 FR 38163, June 26, 2003, Sec. 50.9 was 
amended by adding paragraph (c), effective August 25, 2003. For the 
convenience of the user, the added text is set forth as follows.

Sec.  50.9  National 1-hour primary and secondary ambient air quality 
          standards for ozone.

                                * * * * *

    (c) EPA's authority under paragraph (b) of this section to determine 
that the 1-hour standard no longer applies to an area based on a 
determination that the area has attained the 1-hour standard is stayed 
until such time as EPA issues a final rule revising or reinstating such 
authority and considers and addresses in such rulemaking any comments 
concerning (1) which, if any, implementation activities for a revised 
ozone standard (including but not limited to designation and 
classification of areas) would need to occur before EPA would determine 
that the 1-hour ozone standard no longer applies to an area, and (2) the 
effect of revising the ozone NAAQS on the existing 1-hour ozone 
designations.